CA1329497C - Hydraulic variable lock differential - Google Patents

Abstract

ABSTRACT
A vehicle differential includes a clutch assembly and a hydraulic actuator for selectively preventing relative rotation between a pair of vehicle half axles. The differential assembly has an outer housing rotatably mounting a gear case and ring gear therein. A planetary gear assembly is coupled between the gear case and one half axle. The planetary gear assembly is also coupled to a sun gear which in turn is coupled to the other half axle. The clutch assembly is coupled between the gear case and the sun gear.
An annular manifold is fixedly mounted in the outer housing and sealingly engages an outer surface of the gear case for supplying pressured hydraulic fluid to actuate a piston in a cylinder formed in the gear case which in turn actuates the clutch assembly. The pressure of the hydraulic fluid determines a range of torque differentials for which the clutch assembly will prevent relative rotation between the half axles.

Description

TITLE
H~DRAULIC V~ BLE LOC~ DIFFERENTIAL
BAC~OUND OF T~IE INVENTION
The present ln~ention rel~tes in gelleral to n li~lted slip differential for n vehicle ~nd, in pnrticular, to ~n hydraulically actu~ted vnriable lock dlf~erential.
Early differential mechanisms consisted of a set of planetary gears coupled between two half-shafts of a drive axle. Such a drive axle has the advantages over a solid axle that the wheels of the vehicle can travel at different speeds and equal driving force can be applied to the driving wheels.
However, under certain conditions, this conventional differential has a serious deficiency. For example, if one drive wheel is on a sllppery surfAce, such as ice or ~ud, that wheel will sllp and spin becnuse lts tlre can not grip the road. Consequently, the sllpping wheel cnn 8pply very llttle drlving torque to move the car. The opposite drive wheel, which well may be on a surface that gives good adhesion, can apply no more driving torque than the spinning wheel because the differential delivers only an equal amount of torque to both wheels. Thus, the total driving force can never be more than twlce the amount applled by the wheel with the poorest road adhesion.
Traction is ~lso adversely effected, especially during hard driving, by other conditions that unbalance the weight on the driving wheels. When driving at high speed around a curve, the weight is transferred from the inside wheel to the outside wheel. Hard acceleration coming out of a turn can then cause the inside wheel to spin because it has less weight on it and therefore less road adhesion. Similarly, during any hard acceleration there is propeller shaft reaction torque on the rear axle assembly. When one wheel is partially unloaded and looses part of its traction capability, the loss is not offset by gain on the opposite side because the total can only be twice that of the wheel with the lesser capabLlity.
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' 1329~97

2 1-7S30 The limit~d slip liffer~ntial was lesigned to improve the traction of a vehicle nde1 ad~erse trnction condltions by nllowing the ~ifferential to cratlsmit torqle to the ~le shnfts in ulleqlnl nmoullts wltholt ~nter~erill6 wlth th~
differentinl action on turlls. The most common limited slip differential is the friction type which has clutch nssemblies mounted between the two side gears and the differential case.
In a conventional differential, the side gears and the axle shafts to which they are spllned always turn freely in the case. The added clutches provide a means of transferring torque from the faster spinning (usually slipping) wheel to the slower spinning (usually better adhesion) wheel.
Typically, there nre two clutch pn.ks, each of which is comprised o~ dlsks thnt are splinel to the side genr, and plates that sre tanged to fit into the differential case.
Thus, the disks rotate with the side gear and the plates rotate with the case. The clutches are applied or actuated by two forces. One force is applied by springs compressed between the two side gears which push the slde gears apart, towards the case, and thus keep the plates and dlsks in contact with each other. This force is relatively constant and preloads the clutches. The other force results from the tendency of the pinons and side gears to push themselves :
apart as they turn. This force is applied through the side ~^
25 gears and lncreases the pressure on the plates and disks. -This force becomes greater as the drlving torque transmitted from the pinons to the side gears increases and is therefore a variable force.
The typical limited slip differentlal has a design limit on the amount of torque transfer from the faster to the slower wheel, so th~t the torque on the wheel with good traction is about two and one half times that of the wheel with poor traction. From the above description, several shortcomings of the common limited slip differential are apparent:

~329~97

3 1-~830 1) During turning maneuvers, torque is trnnsferred to the inside wheel at a rate generally proportional to the driving torque. This results in a tendency to understeer.
2) Under conditions where one driving wheel is on a very sl~ppery surface while the other has good traction, the amount of torque that can be transferred is very limited, essentially determined by the preload spring force on the clutch packs.
It is the Lntent of this invention to overcome these shortcomings by providing an externally controllable limited slip differential whose clutch actuating force is not dependent on preload springs or side gear separatlng forces caused by drive llne torque, but rnther is provided by hydrnul~c pressure. This pressure may be regulated as necessary to adJust the different1al from zero to full locking as driving needs dictate.
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SUMMARY OF THE INVENTION
The present invention concerns an hydraulically actuated variable lock differential which utilizes a piston to actuate a multidisk wet clutch to selectively lock the differential.
The clutch pack is mounted within a right side differential case half and the clutch disks are alternately splined to a sun gear and the case half. At the left side of the clutch pack, a pressure plate is fitted and held in position by a snap ring. The right side case half also contains an annular cavity which retains a piston. When hydraulic fluid is injected into the cavity, the piston moves axially to the left and squeezes the clutch disks against the pressure plate thereby providing resistance to relative rotation of the left a~nd right output shafts of the differential.
The hydraulic fluid is provided to the pi~ton cavity by means oi` passages formed in the right case half and leading to an opening on the outer surface of the case half hub. A
ring-shaped manifold ls fitted external to the case half and ~ -.
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13294~ ~

4 l-7S30 suitably mounted so th~t it does not rot~t~. Tllis mnnifold receives hydraulic fluîd under pr~ssure from ~n e~ternnl supply. Tlle mnl~ifold is se~l~d to ~h~ rotntlng ll~b by primary ~nd secon~lnry senls so thnt tlle fluid will enter opening ln the case h~lf hub. A set of passnges in the manlfold rlng allows any hydraulic fluld that leaks past a prlmary seal to be captured by a secondary seal and returned to the external fluld supply.

BRIEF DESCRIPTION OF THE DRAWINGS
The above, as well as other advantages of the present invention, will become readily apparent to those skllled in the art from the followlng detailed description of a preferred embodiment when considered ln the light of the accompanying dr~wings in wllich:
FIG. 1 is a sectional top plan view of a differential assemb1y incorporating the present invsntion;
FIG. 2 is a right side elevational view of the planetary gear wheel assembly shown in FIG. l; -FIG. 3 is a schematic block diagram of the pressured hydraulic fluid supply system for the present invention;
FIG. 4 is a right side elevational view of the hydraulic fluid ~anifold shown in FIG. l;
FIG. 5 is an enlarged cross-sectional view as if taken along the line 5-5 in FIG. 4; and FIG. 6 is an enlarged cross-sectional view as if taken along the line 6-6 of FIG. 4.

. DESCRIPTION OF THE PREFERRED EMBODIMENT
There is shown in FIG. 1 a vehicle differential gear apparatus 11 incorporating an hydraulically actuated variable :
lock differential mechanism in accordance with the present invention. The apparatus 11 includes an outer housing 12 enclosing a rotatable differential gear case 13. The case 13 is formed from a left half case 14 and a right half case 15 which abut at radially outwardly extending flanges 16 and 17 - :
~:. .
.: .

1329~97 respectively. The left half case 14 has an axially outwardly extending hub 18 formed thereon which is rotatably reeained by a tapered roller besring l9 mounted on the interior of the outer houslng 12. Sl~ rly, the right hal~ cnse 15 hns nn outwardly a~iAlly e~tending llub 20 whicll is rotntnbly retained by a tapered roller bearing 21 ~ounted on the interior of the housing 12. The bearings l9 and 21 are mounted on opposite sides of the housing 12 concentrically with a palr of openings through which the lnner ends of a left half axle 22 and right half axle 23 respectively extend.
The half axles 22 and 23 are rotatably supported by a pair of tapered roller bearings 24 and 25 respectively which are mounted in the openlngs formed in the outer houslng 12.
An end of a drlve sh~ft 26 extel~ds through a front w811 of the outer housing 12 nnd terminntes in n drive pinion gear 27. A ring gear 28 is mounted on the outer surface of the rlght half case 15 and abuts the flange 17. The case halves 14 and 15 are attached together and to the rlng gear 28 by a plurality of threaded fasteners 29 which pass through apertures formed ln the flanges 16 and 17 and threadably engage threaded aper~ures in the rlng gear 28.
An annular gear 30 is formed at the base of the flange 16 on the left half case 14 and extends lnslde the right half case 15. The annular gear 30 has a plurality of inwardly facing teeth. The annular gear 30 cooperates with a planetary gear assembly 31 mounted lnside the annular gear 30 and coaxlal with the left half axle 22. Referrlng to FIG. 1 and FIG.2, the planetary gear assembly 31 includes a pair of spaced apart generally circular plates 32 and 33. The left side plate 32 includes a generally tubular hub portion 34 which is coupled to the inner end of the left half axle 22 by cooperating sets of splines. The right plate 33 is formed with an enlarged central opening through which the hub portion 34 extends.
Mounted between the facing inner surfaces of the plates 32 and 33 are a plurality of meshed pairs of planet gears 35 132~i97 6 1-7æ3n and 36. The pl~llet ge~rs 35 n--d 36 ~re ench rotatnbly mounted on An nssocinted one of a plurnlity of plns 3;' whlch extend through apertures for?ned in the plntes 32 and 33 and are retained by nny s~lltnble menns, perm~nent or relensable.
A plurality of web member~ 38 e~tend radially from the axis of rotation of the plates 32 and 33 and are Attsched to the inner surfaces of those plates to form a unit. The gear 35 of each psir of gears is positioned closer to the periphery : :~
of the gear assembly 31 than the gear 36. The outer gears 35 all mesh with the inwardly extending teeth of the annular gear 30. The inner gears 36 all mesh with radially outwardly extending teeth formed on an exterior of a sun gear 39 as shown in FIG. 1. The gears 35 nnd 36 shown in FIC. 1 are shown in cross-section as if taken along the line 1-1 in FIG.
2.
The sun gear 39 is generally tubular in shape and has a center portion 40. An axially extending left end portion 41 extends over and is rotatably mounted on the hub portion 34 :
of the left plate 32. The left end portion 41 is externally toothed to engage the planet gears 36. The teeth extend from an outsr end of the left end portion 41 whlch abuts the inner face of the leit plate 3Z to the right hand edge of the center portion 40. An axially extendlng right end portion 42 is lnternally splined to the inner end of the right half axle .25 23. The outer surface of the right end portlon 42 engages an lnwardly faclng concentric bearlng surface formed in the end of the right half case 15. A radially disposed annular shoulder 43 is formed at the junction of the center portion 40 and the right end portion 42. The shoulder 43 bears ~: :
against a radially extending annular surface 44 formed inside the rlght half case 15. -An hydraulically operated multldls?k wet clutch assembly :
45 is positioned inside the right half case 15 concentric with and mounted on the center portion 40 of the sun gear 39.
The clutch assembly 45 provides a variably controllable reslstance to the relative rotation between the left half ' 1329~g7 7 1- 7s3n axle 22 And the ri~ht ~nlf a~le 23. The clutcll nssembly 45 includes A wet clutch p~c~ comprlsed of ~ plurAllty of l~terally movable annular cl~ltch dis~s concentrlcally stacked together side by slde. Alternnte disks 46 are slidably keyed to the right half case 15 and are linked to the left hslf axle 22 through th~ right half case 15, the left half case 14, the annular gear 30 and the planetary gear assembly 31.
The alternate disks 46 alternate with a plurality of intermediate disks 47 which are slidably keyed by means of radially inwardly pro~ecting teeth which engage the teeth formed on the center portion 40 of the sun gear 39.
The left end of the clutch pack of the clutch assembly 45 abuts an annular pressure plate 48. The pressure plate 48 is prevented from Axial movement to the left by A snap right 49 which engA~es an inw~rdly fncing nntlulAr groove formed in the interior surface of the right half case 15 ad~acent the pl~netary gear assembly 31. The right end of the wet clutch pack abuts an annular piston 50 retained in an annular piston chamber 51 formed in an interior surface of a wall of the right half case 15 and sealed with O-rings on its outer and inner diameters. The piston 50 is free to move axially ln the pi~ton chamber 51 to apply pressure to the wet clutch pack tending to force it against the pressure plate 48.
The right end of the piston chamber 51 has an orifice formed therein which is in fluid communication with an hydraulic fluid passageway 52 formed in the wall of the right half case 15. The opposite end of the fluid passageway 52 is ln fluid communication with an orifice which opens to an :~
external surface of the right half case 15 at an inwardly facing surface of a manifold 53.
The manifold 53 is shown in greater detail in FIG. 4 through FIG. 6. The manifold 53 has a radially extending threaded inlet 54 formed in an outer surface thereof for connection to an hydraulic fluid supply line and fitting ~not shown). The threaded inlet S4 is in fluid communication w~th an inwardly facing annular channel 55. The channel 55 faces 1~9497 S 1^7S30 ~ -the e~terior stlrfnce of tl~ rl~l~t l-nlf Cl-S~ 15 nnd ls sonl~d along opposite sides by a pnir of n~n~llnr llp seals 56. The lip seals 56 form a primary seal for the hydraulic fluid ~-path. If any of the hydraulic fluid should leak past the lip seals 56, it can be returned to the hydraulic fluid supply through a threaded outlet 57 formed in the exterior surface of the manifold 53. The threaded outlet 57 is adapted to be connected to a threaded fitting and hydraulic line (not shown) to return hydraulic fluid to a reservoir as will be discussed below.
The threaded outlet 57 is connected to a pair of radially extending passages 58 spaced between the threaded outlet 57 and the opposite side surfaces of the manlfold 53.
The passages 58 e~tend from the outer peripheral surface to the lnner peripheral surface of the mnnifold 53 and are closed at thelr outer ends by threaded plugs 59. A pair of 0-ring (or other suitable) seals 60 are positioned in annular `
grooves formed in the inner peripheral surface of the manifold 53 and are positioned between the lip seals 56 and 20 the side surfaces of the manifold 53. The lip seals 56 and ~`
the 0-ring seals 60 are exposed to opposite sldes of the inner end of the radial passages 58. Thus, any hydraulic `
fluid which leaks from the annular channel 55 past the lip seals 56 will enter the passages 58 and will be prevented by the 0-rin~ seal 60 from leaking outside the manifold 53. The threaded outlet 57 is in fluid communication with the radial passages 58 through an axially extending passage 61 extending -~
from one side surface of the manifold 53 to the passage 58 ad~acent the opposite side surface. The outer end of the passage 61 is sealed with a threaded plug 62. The manifold 53 can be mounted to the outer housing 12 by any suitable -means to prevent rotation. Thus, the right half case 15 rotates within the central opening of the manifold 53 against the lip seals 56 and the 0-rings 60. The 0-ring seals 60 ~;
function as a secondary seal which enables any hydraulic fluid which leaks past the primary seal to be returned to the .' 132g~7 e~ternal hydraulic fluid S~lr~ly~
There is shown in FIG, 3 n schemntic block diagsam of ~n hydraulic fluid supply and control system for use with the present lnvent~on. An hydraulic fluid reservoir 63 ls connected to a fluid supply line 64 below the fluid level in the reservolr 63. The fluid supply line 64 is connected to an inlet of an hydraulic pump 65 of the unidirectional, fixed displacement type. An outlet of the hydraullc pump 65 is connected to a system supply line 66. The outlet of the pump 65 is also connected through an ad~ustable pressure relief valve 67 to a return line 68 which terminates in the reservolr 63.
An accumulator 69 ls connected to the system supply line 66. This accumulator serves as a reservoir of hydraulic flu~d under pressure to prevent frequent on/off cycllng of the pump 65. A pressure-sensitive switch 70 controls the operatlon of the pump 65. The limits of switch 70 are set to obtain the desired hydraulic fluid pressure in supply line 66 ~, and accumulator 69.
The supply line 66 is connected to one inlet of a three-way normally closed solenoid actuated valve 71. An outlet of the valve 71 is connected by a return line 72 to the reservoir 63. An inlet/outlet of the valve 71 is connected by a line 73 to the threaded inlet 54 on the manifold 53.
The hydraullc fluid exits from the manifold 53 into the passageway 52 and from there into the piston chamber 51 to act~ate the piston 50 which in turn actuates the clutch assembly 45. Any fluid which passes the lip seals 56 of the primary seal is trapped by the secondary O-ring seals 60 and ~-exits the manifold 53 through the threaded outl'et 57. A
return line 74 is co,nnected to the threaded outlet 57 and terminates at the reservoir 63.
When the valve 71 is actuated, pressured fluid in the line 66 passes through the valve to the line 73 and flows to the piston chamber through the path described above. The clutch actuating fluid pressure is released when the 1329~97 l-7S30 energizing power is removed from the solenoid associated with the valve 71.
Hydraulic fluid in the piston chamber 51 can now Elow backward through the fluid passageway 52, through the manifold 53, line 73, ~alve 71, and return line 72 to the reservoir 63. The release of pressure in piston chamber 51 reduces the force on piston 50 to essentially z.ero, allowlng the plates in clutch pack 45 to rotate freely against each other. Thus, when the solenoid valve 71 i9 not energized, the differential behaves essentially as an open or free differential.
As the piston 50 is actuated by the application of pressured hydraulic fluid, the clutch disks 46 and 47 are ~ ;
squeezed together against the pressure plate thereby ~ -providing resistance to relative rotation between the left half axle 22 and the right half axle 23. Thus, the dLfferential will be locked for a range of torque wh~ch is the difference in the torques applied to tha half axles. The torque range will be from zero to an upper limit determined by the torque at which the clutch slips. This upper limit i8 related to the hydraulic fluid pressure.
In this embodiment of the hydraulic supply, the degree oi locking is set by the limits set on pressure switch 70.
The solenoid valve 71 could be controlled by an electronic circuit, not shown, that activates valve 71 when wheel spin occurs. It should be realized that other embodiments of the hydraulic supply are possible within the scope of this invention. For e~ample, if the solenoid valve 71 were replaced by an electro-hydraulic proportional or servo valve, it would be possible to electronically vary the pressure in llne 73 from zero to the value of pressure in line 66, as set by switch 70. This would permit the locking torque of the differential to be varied as necessary to meet driving requirements.

132g~97 In accordancs with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced S otherwise than as specifically illustrated and described without d~parting from its spirlt or scope. ~:

Claims (9)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A variable lock vehicle differential apparatus for driving a pair of vehicle half axles from a drive shaft, comprising:

an outer housing;

a differential gear assembly in a case rotatably mounted in said housing and adapted to be coupled between a vehicle drive shaft and a pair of vehicle half axles, said differential gear assembly including a sun gear coupled to one of said half axles and an annular gear attached to said case and coupled to a planetary gear assembly mounted in said case and having a first plurality of planet gears each coupled for rotation by said case, a second plurality of planet gears each coupled for rotation by an associated one of said first plurality of planet gears and coupled to rotate said sun gear, and a hub portion coupled to the other one of said half axles, said sun gear and said annular gear rotating relative to one another during relative rotation between said half axles;

a clutch assembly coupled between said case and said sun gear for selectively resisting relative rotation between said case and said sun gear upon actuation;

actuating means for selectively hydraulically actuating said clutch assembly; and a manifold for supplying hydraulic fluid to said actuating means, said manifold mounted inside said outer housing and having an annular body for rotatably accepting said case, said manifold adapted to be connected to a source of hydraulic fluid under pressure, said manifold having an inwardly facing annular channel formed therein and an inlet formed in said annular body and in fluid communication with said channel, said channel being in fluid communication with said actuating means, a pair of lip seals positioned on opposite sides of said channel and sealingly engaging an outer surface of said case to function as a primary seal, a pair of O-ring seals retained in grooves formed in said annular body and positioned outwardly of said lip seals to function as a secondary seal sealingly engaging said outer surface of said case and an outlet formed in said annular body and in fluid communication with an inwardly facing surface of said manifold positioned between said lip seals and said O-ring seals whereby fluid in said channel which leaks past said lip seals flows to said outlet.

2. The apparatus according to claim 1 wherein said actuating means includes an annular piston mounted in a cylinder formed in said case and coupled to said clutch assembly and a passageway formed in said case for fluid communication between said manifold and said cylinder whereby pressured fluid flows from said manifold through said passageway and into said cylinder to actuate said piston and said clutch assembly and relative rotation between the half axles is prevented.

3. The apparatus according to claim 1 wherein said clutch assembly includes a plurality of alternate disks slidingly coupled to said case and each positioned between an adjacent pair of a plurality of intermediate disks slidingly coupled to said sun gear.

4. The apparatus according to claim 3 wherein said clutch assembly includes an annular pressure plate positioned at an opposite end of said disks from said actuating means and a snap ring engaging a groove formed in said case and abutting said pressure plate.

5. In a differential apparatus for driving a pair of vehicle half axles including an outer housing, a gear case rotatably mounted in the housing, a ring gear attached to the gear case and adapted to be rotated by a vehicle drive shaft, a differential gear assembly mounted in and coupled to the gear case and adapted to be coupled to a half axle and including a sun gear adapted to be coupled to another half axle, and means for preventing relative rotation between the gear case and the sun gear comprising:
a clutch assembly coupled between the gear case and the sim gear;
an hydraulically operated clutch actuating means coupled to said clutch assembly; and an hydraulic fluid manifold in fluid communication with said actuating means, said manifold mounted in the housing and sealed against an outer surface of the gear case, saod manifold being formed with an annular body having an inwardly facing annular channel formed in an inner wall thereof and an inlet in fluid communication between said annular channel and an exterior surface of said manifold, said inlet adapted to be connected to a source of pressured hydraulic fluid, a primary seal having a pair of annular lip seals positioned on opposite sides of said channel for sealingly engaging an outer surface of the gear case, a secondary seal having a pair of 0-ring seals retained in annular grooves formed between said channel and sides of said annular body for blocking the flow of any hydraulic fluid which leaks from said channel past said lip seals, an outlet formed in said exterior surface of said annular body, and a pair of passages formed in said annular body in fluid communication between said outlet and said inner wall of said annular body between said primary seal and said secondary seal.

6. The means for preventing relative rotation according to claim 5 wherein said clutch assembly includes a plurality of clutch disks stacked between a pressure plate and said actuating means, at least one of said disks slidingly coupled to the gear case and at least another one of said disks slidingly coupled to said sun gear and abutting said one disk, said pressure plate being coupled to the gear case.

7. The means for preventing relative rotation according to claim 5 wherein said actuating means includes an annular piston axially movable in a cylinder formed in the gear case and a passageway formed in the gear case in fluid communication between said cylinder and said manifold.

8. A variable lock differential apparatus for driving a pair of vehicle half axles from a drive shaft, comprising:
an outer housing;
a gear case and attached ring gear adapted to be coupled to and rotated by a vehicle drive shaft;
a planetary gear assembly mounted in said gear case and having a first plurality of planet gears each coupled for rotation by said case, a second plurality of planet gears each coupled for rotation by an associated one of said first plurality of planet gears, and a hub portion adapted to coupled to rotate a first half axle;
a sun gear coupled for rotation by said second plurality of planet gears and adapted to be coupled to rotate a second half axle;
a clutch assembly coupled between said gear case and said sun gear;
a piston retained in a cylinder formed in said gear case and coupled to said clutch assembly; and means for supplying fluid under pressure to said cylinder to actuate said piston and said clutch for resisting relative rotation between said gear case and said sun gear, said means for supplying fluid including an annular manifold fixedly mounted in said outer housing and including an inwardly facing annular channel, a primary seal for sealingly engaging an outer surface of said gear case, an inlet in fluid communication between said channel and an exterior surface of said manifold and adapted to be connected to a source of fluid under pressure whereby relative rotation between the half axles is prevented in a predetermined range of torque which is the difference in the torques applied to the half axles and is related to the pressure of the fluid supplied, a secondary seal for sealingly engaging said exterior surface of said gear case, said secondary Real positioned between said primary seal and a side surface of said manifold, and an outlet formed in said manifold and in fluid communication between said exterior surface of said manifold and a portion of said manifold between said primary seal and said secondary seal for removing fluid which leaks from said channel past said primary seal.

9. An said for supplying pressured fluid to an hydraulic actuator for a variable lock vehicle differential apparatus for driving a pair of vehicle half axles from a drive shaft, comprising:
a manifold having a surface for slidably engaging an exterior surface of a case for a variable lock differential gear assembly rotatably mounted in a housing and adapted to be coupled between a vehicle drive shaft and a pair of vehicle half axles, said manifold adapted to be mounted in the housing;
an inlet formed in said manifold and adapted to be connected to a source of hydraulic fluid under pressure;
a channel formed in said manifold surface and connected to said inlet for providing hydraulic fluid under pressure to an hydraulic actuator mounted in the case through a passageway formed in the case;
and seal means positioned in said manifold surface on opposite sides of said channel for sealingly engaging the exterior surface of the case to prevent leaking of hydraulic fluid from said channel.